1. Field of the Invention
The present invention relates to a method of manufacturing a lithium-ion secondary battery positive electrode, a method of manufacturing a lithium-ion secondary battery, a lithium-ion secondary battery positive electrode, and a lithium-ion secondary battery.
2. Related Background Art
It is desirable for lithium-ion secondary batteries to secure homogeneity within an electrode in order to improve the electrode capacity, cycle characteristics, and reliability. The homogeneity within an electrode seems to be secured when a coating material for forming the electrode has favorable dispersibility. When the productivity of electrodes is taken into consideration, it will be desirable if the dispersibility of the coating material is not deteriorated with time by aggregations of components contained therein and the like.
Since the deterioration in dispersibility of a coating material with time begins immediately after making the coating material, a method of keeping a network structure in the coating material by increasing the amount of binders contained in the coating material has been under consideration as a measure for suppressing the deterioration with time (see, for example, Japanese Patent Application Laid-Open No. 2000-021408). This increases the amount of binders which do not contribute to electric characteristics, whereby problems in cell characteristics such as decreases in capacity and increases in resistance value may occur. From the viewpoint of keeping a network structure, increasing the amount of conductive carbon may be considered. This is effective in lowering the resistance value, but may decrease the amount of active materials contained, thus reducing the capacity and making the coating film structure fragile, thereby failing to improve the reliability.
As the binders added to the coating material, those made by suspension polymerization have been in wide use (see, for example, Japanese Patent Application Laid-Open Nos. 2004-087325, 2005-310747, 2008-045096, and 2008-088330 and Japanese Domestic Republication of PCT International Application Laid-Open No. 2005-116092).